Cyanobacteria refer to

Options

A. Autotrophic prokaryotes with character- istic bluegreen pigments
B. Bacteria infecting the cyanophycean al- gae
C. Viruses infecting bluegreen alagae
D. Cynophycean members infecting bac- teria

Answer

### Step-by-Step Solution

1. **Understanding Cyanobacteria**:
- Cyanobacteria are a group of photosynthetic bacteria that are often referred to as blue-green algae. They belong to the kingdom Monera and are classified as prokaryotes.

2. **Characteristics of Prokaryotes**:
- Prokaryotes are organisms that lack a true nucleus and membrane-bound organelles. This is a fundamental characteristic that distinguishes them from eukaryotes.

3. **Mode of Nutrition**:
- Cyanobacteria are autotrophic, meaning they can produce their own food through photosynthesis. They utilize sunlight and contain pigments that allow them to perform this process.

4. **Presence of Pigments**:
- The blue-green color of Cyanobacteria is due to the presence of specific photosynthetic pigments, which are crucial for their ability to photosynthesize.

5. **Evaluating the Options**:
- **Option A**: Autotropic prokaryotes with characteristic blue-green pigments. This is correct as it accurately describes Cyanobacteria.
- **Option B**: Bacteria infecting the cyanophysician algae. This is incorrect; Cyanobacteria are not bacteria that infect algae.
- **Option C**: Viruses infecting blue-green alga. This is incorrect; Cyanobacteria are not viruses.
- **Option D**: Cyanophysician members infecting bacteria. This is also incorrect; Cyanobacteria do not infect bacteria.

6. **Conclusion**:
- The correct answer is **Option A**: Autotropic prokaryotes with characteristic blue-green pigments.